Well bit



Alllg- 12, 1941v 1'.. A. cRElGHToN Y 2,252,168

ticularly effective Patented Aug. 12, 1941 WELL BIT Thomas A. Creighton,

Long Beach, Calif., assigner of one-half to Martha H. Wright, LosAngeles,

Calif.

Application June 17, 1940, Serial No. 340,959

(Cl. Z55- 61) 6 Claims.

This invention relates to Well drilling tools and relates moreparticularly to a well bit for use in the rotary method of welldrilling. A general object of this invention is to provide a simple andpractical rotary Well drilling bit embodying a parinner cutting means orcore Cutting means.

With the present day rotary well drilling methods the circulation fluidis delivered to the drilling tool in substantial volumes and at highpressures and drag type drilling bits have been developed having asingle central port of large diameter for discharging the fluid at thelower end of the bit to assure a thorough flushing action and to providefor the eroding of the earth formation by the fluid. The large centralfluid port is located Within the annular series of principal cuttingblades leaving a substantial area that is not acted on by the principalblades. For this reason it has been necessary to provide core breakingmeans or inner cutting means for cutting away the core of earthformation that otherwise would remain in the center of the bore. Thesecore breaking means or core cutting means have materially interferedwith the free discharge of the circulation uid from the single dischargeport reducing the efficiency of the tools.

Another object of this invention is to provide a Well drilling bit orpilot bit having a single central fluid discharge port and characterizedby a l cutting means for cutting away the core or central portion of theearth formation, which does not interfere with cr appreciably reduce thefree discharge of the fluid from the central port.

Another object of this invention is to provide a well bit of thecharacter referred to in which the inner cutting means comprises asingle cutting part or blade formed and arranged to entirely cut awaythe earth formation remaining Within the zone of operation of the outerblades.

Another object of this invention is to provide a well bit of thecharacter referred to in which the inner blade is formed and located sothat the core cannot enter the fluid discharge port and so that thecuttings from the core cannot choke or enter the port.

Another object of thisinvention is toprovide a bit of the charactermentioned in which the inner cutting blade may be inexpensively embodiedin the tool as a rigid permanent element.

Another object of this invention is to provide `a well bit of thecharacter referred to including a choke bushing or bean adapted to bepassed down through the drilling string to the bit to cause thecirculation fluid to discharge at an increased velocity so that it ismore effective in its eroding action.

A further object of this invention is to provide a Well bit of thecharacter referred to in which the inner cutting blade forms a stop andsupport for the choke bushing or bean serving tosupport the bean Whereit is most efficient in its nozzle action.

The various -objects and features of my invention will be fullyunderstood from the following detailed description of a typicalpreferred form and application of the invention, throughout whichdescription reference is made to the aocompanying drawing, in which:

Fig. l is a side elevation of the improved Well bit of the invention.Fig. 2 is a vertical detailed sectional View taken substantially asindicated by line 2-2 on Fig. 1 with the upper portion in sideelevation. Fig. 3 is a transverse detailed sectional view taken asindicated by line 3--3 on Fig. 2 and Fig. 4 is a fragmentary verticaldetailed sectional View of the lower portion of the bit showing thechoke bushing or bean in position in the port.

The present invention is capable of embodiment in drilling bits forforming full sized well bores and in pilot bits to be run below reamersor bore enlarging tools. The tool herein described may be consideredeither a drilling bit or a pilot bit and where I herein employ the termbit it is to be understood as meaning either a drilling bit or a pilotbit.

The Well drilling bit of the present invention may be said to comprise,generally, a body I 0 having a central fluid port II, outer cuttingblades I2 on the body I0, an inner cutting blade I3 on one of the bladesI2 and a choke bushing or bean I4 adapted to be run into the port I I.

The bit body It] is adapted to be secured to the lower end of a welldrilling string and serves to carry the several cutting parts. Inpractice the body It may be an elongate generally cylindrical memberprovided at its upper end with suitable means for facilitating itsconnection with the drilling string4 In the particular case illustratedthe upper end of the body I0 is provided with a tapered screw threadedpin I5 to be threaded into a part of the drilling string. The lower endportion of the body I0 preferably tapers or curves downwardly andinwardly to a flat horizontal end face I6. The central fluid passage orport II extends longitudinally through the body ID from one end to theother. The upper end of the port I I, occurring at the top of the pinI5, is adapted to communicate with the interior of the drilling stringand the lower end of the port II discharges downwardly at the end faceI6. In accordance with the invention the port I I is uniform in diameterand is preferably cylindrical. I prefer to make the port II of largediameter or fluid capacity so that it may handle a substantial volume offluid. As will be later described, the outlet end of the port II may berestricted or provided with a nozzle means where operating conditionsmake this desirable.

The outer cutting blades I2 project from the lower portion of the body Ito cut or form the outer part of the well bore. There are two or morecircumferentially spaced outer cutting blades I2. In the constructionillustrated there are three equally spaced blades I2. The blades I2 areformed on the lower rounded portion of the body I0 and project asubstantial distance downwardly from the body. The outer blades I2 alsoproject outwardly or laterally from the body I0 to provide ampleclearance for the body and the drilling string. The blades I2 aresubstantially vertical although it is preferred to have them slopedownwardly and forwardly relative to the right hand direction ofrotation. The forward faces II of the blades I2 are flat and aresubstantially radial relative to the central longitudinal axis of thetool. The rear faces of the blades I2 may be convex or rounded and theirlower parts curved downwardly and forwardly to join the forward facesI'I at lower cutting edges I8. rIhe outer edges or reaming edges I9 ofthe blades I2 may be straight and substantially vertical. 'Ihe inneredges or sides 22 of the blades I2 are substantially vertical and may befiat, as illustrated. In practice the inner faces 20 of the blades I2may occupy planes tangential to a circle of substantially the samediameter as the port I I and concentric with the port. Because of thisdisposition of the inner edges or faces 29 the blades I2 do notinterfere with the free discharge of fluid from the port II and areeroded or cut out to a minimum extent by the fluid discharged from theport. The main or outer cutting blades I2 are preferably quite long tobe long wearing. The blades I2 formed and arranged as above described,assure the free passage of fluid between them so that there is a minimumtendency of the bit to ball up with mud and cuttings.

The inner cutting blade I3 is provided to cut away the central portionof the earth formation left by the outer blades I2. It is an importantfeature of the invention that the blade I3 is formed and positioned sothat it does not interfere with the free discharge of fluid from theport II. In accordance with the invention the blade I3 is a partintegrally or at least rigidly formed or provided on an inner face 20 ofone of the outer blades I2. The core cutting blade I3 is locatedentirely below the lower face I of the body III and, therefore, isentirely below the port II where it cannot interfere with the fluiddischarge from the port. It is preferred to shape and proportion theblade E3 so that it projects inwardly to or immediately adjacent thecentral longitudinal axis of the tool to entirely cut away the earthformation that may remain between the outer blades I2.

'The shape of the inner blade I3 may be varied considerably, however, itis preferred to form or shape the blade substantially as illustrated. Inthe construction illustrated the upper edge 22 of the blade I3 slopes orcurves inwardly and downwardly relative to the central axis of thetool.The lower edge or cutting edge 23 is substantially aataies straight andextends horizontally to join the curved edge 22 at or immediatelyadjacent the central vertical axis of the tool. The forward face 2li ofthe blade I3 is flat and may be vertical, as illustrated, or may lie inthe sloping plane occupied by the adjacent forward face I'I of thecutting blade I2, which carries the blade I3. As best illustrated inFig. 3 of the drawing, the rear side of the blade I3, relative to thedirection of rotation of the bit, slopes outwardly and rearwardly sothat the blade is of substantial thickness where it merges with itscarrier blade I2. The upper edge of the blade I3 is beveled to shed ordivert the down flowing fluid to the best advantage. The cutting edge 23is preferably provided with hard metal or other abrasion resistingmaterial.

The inner blade I3 formed and arranged, as just described, is effectivein entirely cutting away the core of earth formation with a minimum ofinterference to the free flow of fiuid from the port I I. The blade I3is below the port I I so that it does not interfere with the fluiddischarge and so that the cuttings from the core cannot enter the port.The blade I3 occupies substantially the same vertical plane as itscarrier blade I2 so that its presence beyond the end of the port IIoffers practically no interference to the free flow of uid between theblades I2 and so that there is no tendency for the cuttings toaccumulate about it. The fluid flushing past the forward and rear facesof the carrier blade I2 fully clears the inner blade I3 of all cuttings.

The choke bushing or bean III is not always essential or required butmay be desirable in situations where it is necessary or preferred toincrease the velocity of the circulation fluid as it discharges from theport II. When the bit is in in the well the bushing or bean Ill isadapted to be lowered or dropped through the drilling string to assumean operative position in the port II. In other cases the bean I4 may beinstalled in the bit before the bit is run into the well. The bushing orbean III is a tubular element formed of erosion and abrasion resistingmaterial and is proportioned to rather accurately t the port II. Theinside diameter of the bean I4 may be varied to increase the Velocity ofthe circulation fluid to any selected extent. The lower end 26 of thebushing or bean I4 may be rounded to guide the bean through the drillingstring and is adapted to engage and rest on the upper edge 22 of theinner lblade I3. If desired, the upper edge 22 of the blade I3 may beformed with a seat or face to receive the bean I4. As shown in Fig. 4 ofthe drawing the lower end 25 of the bean III engages on the upper edge22 of the blade I3 at or immediately adjacent the lower face I6 of thebody III so that the bean Ill is substantially entirely confined to theport II. The upper end 21 of the bushing or bean III may be tapereddownwardly and inwardly to direct the fluid through the bean.

In the use or operation of the bit provided by this invention the body Iis secured to the lower end of the drilling string so that the bit isoperated inthe lower end of the well bore. When the drilling string isrotated and fed downwardly the outer cutting blades I2 cut the well boreor the pilot bore to gauge, serving to drill away the major portion ofthe earth formation. The inner cutting blade I3 operates to remove orcut away the central core of earth formation that may remain within theseries of outer blades I2.

'The inner blade I3 projects inwardly to or adjacent the centralvertical axis of the bit to entirely cut away the core. The blades I2and I3 may be formed of or faced with hard cutting and abrasionresistant material to be long wearing and to be effective in theirdrilling action. The hard or hardfaced blades I2 and I3 are resistant tothe abrasive and erosive action of the circulation fluid discharged fromthe port I I.

During the drilling operation circulation fluid is continuously pumpedthrough the drilling string under pressure to discharge from the portII. The circulation fluid discharging from the port II impinges againstthe bottom of the well bore to have an erosive action on the same andpasses upwardly and outwardly between the bla-des I2 to clear the bladesof cuttings. The core cutting blade I3 is entirely below the port II andoccupies the same vertical plane as its carrier blade I 2 so that itdoes not interfere with or restrict the discharging fluid from the portI I. The fluid discharging downwardly around the blade I3 fully flushesthe blade and as the blade is unconfined and wholly outside of the portII and the body I there is no tendency for cuttings to accumulate on theblade I3. Thus, the cuttings from the central core of earth formationcannot accumulate to restrict or interfere with the free discharge ofthe circulation fluid. It will be observed that the blade I3 arranged onthe inner face 20 of a blade I2 does not interfere with the passage ofthe circulation fluid across the faces of the blades I2 and does notcause the cuttings, mud, etc. to accumulate on the blades I2.

If it is desired to increase the velocity of the fluid discharging fromthe port I I the choke bushing or bean I4 is dropped or lowered throughthe drilling string. The bean I4 passes down through the port I I andcomes to rest against the blade I3. The bean I4 may, of course, bepositioned in the bit before the bit is run into the well. The upperedge 22 of the blade I3 forms a seat or support for the bean I4 servingto hold or stop the bean where its lower end 26 is immediately adjacentthe lower end of the body Ill. With the bean I4 is positioned againstthe blade I3 it beans down the fluid flow increasing the velocity of thefluid discharged from the port. This may materially aid in the drillingaction and may assure the better flushing of the cutting parts. Ifdesired, the bean I4 may be removed at any time for replacement.

Having described only a typical preferred form and application of myinvention, I do not wish to be limited or restricted to the specificdetails herein set forth, but wish to reserve to myself any variationsor modifications that may appear to those skilled in the art or fallwithin the scope of the following claims:

Having described my invention, I claim:

1. A rotary well bit comprising a body having a substantially centralfluid port discharging at its lowerend, outer cutting parts projectingfrom the lower end of the body and spaced from the central vertical axisof the body to leave a central core of earth formation, and a singleinner cutting blade carried by one of the outer cutting parts andprojecting inwardly toward said axis below the lower end of the body tocut away said core, said blade having a beveled downwardly and inwardlysloping upper edge to shed the fluid discharged by the port and having alower cutting edge which is transverse of the longitudinal axis of thebit.

2. A rotary well bit comprising a body having a substantially centralfluid port discharging at its lower end, spaced outer cutting bladesprojecting from the lower end of the body and spaced from the centralvertical axis of the body to be clear of said port, the outer bladeslying in spaced generally vertical planes, and a single inner bladeprojecting inwardly from one outer blade below the lower end of the bodyto cut away the core of earth formation left by the outer blades, theinner blade lying within the same generally vertical plane as the outerblade which carries it to offer no interference to the passage of fluidbetween the outer blades.

3. A rotary well bit comprising a body having a substantially centralfluid port discharging at its lower end, spaced outer cutting bladespropecting from the lower end of the body and spaced from the centralvertical axis of the body to be clear of said port, the outer bladeslying in spaced generally vertical planes, and a single inner bladeprojecting inwardly from an outer blade below the lower end of the bodyto have its inner end adjacent said axis, the inner blade having itsupper edge beveled to shed the fluid from said port with a minimum ofinterference and having a lower cutting edge to cut away the earthformation left within the series of outer blades.

4. A well bit for use on a tubular rotary well drilling stringcomprising a body to be secured to the lower end of the string andhaving a fluid passage communicating with the string to receive thecirculation fluid therefrom, said passage discharging at the lower endof the body, cutting parts on the lower end of the body, one of thecutting parts projecting inwardly below the lower end of the passage,and a choke bushing adapted to move down the string and through saidpassage to rest on said cutting part in a position to form a nozzle forsaid passage.

5. A well bit for use on a tubular rotary well drilling stringcomprising a body to be secured to the lower end of the string andhaving a fluid passage communicating with the string to receive thecirculation fluid therefrom, said passage discharging at the lower endof the body, an outer cutting blade projecting from the lower end of thebody, and spaced from the central vertical axis of the body to be clearof said passage, an inner cutting blade projecting from the inner edgeof the outer blade below the lower end of the 'body to cut away the coreof earth formation left by the outer blade, and a choke bushing restingon the inner blade where it forms a nozzle at the lower end of thepassage.

6. A well bit for use on a tubular rotary well drilling stringcomprising a body to be secured to the lower end of the string andhaving a fluid passage communicating with the string to receive thecirculation fluid therefrom, said passage discharging at the lower endof the body, spaced outer cutting blades projecting from the lower endof the body, the outer blades having their inner edges spaced from thecentral vertical axis of the body to bel clear of said passage, a chokebushing for said passage, and an inner blade projecting inwardly fromthe inner edge of an outer blade to cut away the core left by the outerblades and adapted to support said choke bushing in its operativeposition.

THOMAS A. CRElGI-ITON.

